The present invention relates to a chamfering cutting tool insert particularly useful for the milling of plates intended for manufacturing of tubes for pipelines for crude oil, natural gas or the like.
Pipelines are frequently used to transport fluid products for substantial distances, with oil and gas transmission pipelines being but two well-known examples. Such pipelines are generally constructed of individual pipe sections that are joined together by welding.
Individual pipe sections are formed from huge plates on the order of 4 m×12 m with a thickness of 25 mm, of low alloyed steel and welded longitudinally.
Separate lengths of pipe are typically interconnected by electric-arc welding and many types of welding techniques are used or proposed in the art for that purpose.
The plates are machined to obtain a chamfer suitable for the subsequent welding of the individual sections as well as the welding together of separate pipe sections.
The machining of the plates to obtain the desired character is made in large milling machines with cutters having a diameter of from about 600 to 1200 mm, provided with 40-80 inserts of rectangular shape tangentially mounted with dimensions of 32×20×8 mm. Normally inserts of coated cemented carbide grade tools are used.
It is important to obtain long tool life and minimise the tool change frequency in order to reduce the cost. The criteria for the operation are sufficient surface finish and little or no structure deformation. It is important to create a surface finish that does not disturb the welding process.